Biodistribution and Uptake of Liposomes In Vivo

Liposomal AntagomiR-155-5p Restores Anti-Inflammatory Macrophages and Improves Arthritis in Preclinical Models of Rheumatoid Arthritis

OBJECTIVE

We previously reported an increased expression of microRNA-155 (miR-155) in the blood monocytes of patients with rheumatoid arthritis (RA) that could be responsible for impaired monocyte polarization to anti-inflammatory M2-like macrophages. In this study, we employed two preclinical models of RA, collagen-induced arthritis and K/BxN serum transfer arthritis, to examine the therapeutic potential of antagomiR-155-5p entrapped within PEGylated (polyethylene glycol [PEG]) liposomes in resolution of arthritis and repolarization of monocytes towards the anti-inflammatory M2 phenotype.

METHODS

AntagomiR-155-5p or antagomiR-control were encapsulated in PEG liposomes of 100 nm in size and -10 mV in zeta potential with high antagomiR loading efficiency (above 80%). Mice were injected intravenously with 1.5 nmol/100 μL PEG liposomes containing antagomiR-155-5p or control after the induction of arthritis.

RESULTS

We demonstrated the biodistribution of fluorescently tagged PEG liposomes to inflamed joints one hour after the injection of fluorescently tagged PEG liposomes, as well as the liver's subsequent accumulation after 48 hours, indicative of hepatic clearance, in mice with arthritis. The injection of PEG liposomes containing antagomiR-155-5p decreased arthritis score and paw swelling compared with PEG liposomes containing antagomiR-control or the systemic delivery of free antagomiR-155-5p. Moreover, treatment with PEG liposomes containing antagomiR-155-5p led to the restoration of bone marrow monocyte defects in anti-inflammatory macrophage differentiation without any significant functional change in other immune cells, including splenic B and T cells.

CONCLUSION

The injection of antagomiR-155-5p encapsulated in PEG liposomes allows the delivery of small RNA to monocytes and macrophages and reduces joint inflammation in murine models of RA, providing a promising strategy in human disease.

In vivo fate of liposomes after subconjunctival ocular delivery

Subconjunctival administration of nanocarriers presents an alternative drug delivery strategy to overcome blood-ocular barriers to enhance drug bioavailability to specific parts of the eye. Using fiberoptic Confocal Laser Microendoscopy (CLM) and radiotracing, we describe the effects of charge, size, cholesterol content and lipid saturation on the ocular and corporal distribution of liposome nanocarriers in live mouse models. Positively charged or large (>250 nm) liposomes exhibit sustained ocular residence times in and around the injection site; cholesterol loading slows down this clearance, whereas lipid saturation accelerates clearance. Neutral, negatively charged, or smaller sized liposomes distribute to the limbus, rich in stem cells and blood capillaries. Differential lymphatic and systemic clearance from the eye to corporeal tissues was also observed across formulations. These results demonstrate the need to optimize liposome design for control over temporal and spatial nanocarrier bioavailability and clearance from the eye for improved efficacy and safety of ocular therapeutics.

PEG-Peptide Inhibition of Scavenger Receptor Uptake of Nanoparticles by the Liver

PEGylated polylysine peptides represent a new class of scavenger receptor inhibitors that may find utility at inhibiting DNA nanoparticle uptake by Kupffer cells in the liver. PEG-peptides inhibit scavenger receptors in the liver by a novel mechanism involving in situ formation of albumin nanoparticles. The present study developed a new in vivo assay used to explore the structure-activity-relationships of PEG-peptides to find potent scavenger receptor inhibitors. Radio-iodinated PEG-peptides were dosed i.v. in mice and shown to saturate liver uptake in a dose-dependent fashion. The inhibition potency (IC₅₀) was dependent on both the length of a polylysine repeat and PEG molecular weight. PEG_30kda-Cys-Tyr-Lys₂₅ was confirmed to be a high molecular weight (33.5 kDa) scavenger receptor inhibitor with an IC₅₀ of 18 μM. Incorporation of multiple Leu residues improved potency, allowing a decrease in PEG MW and Lys repeat, resulting in PEG_5kda-Cys-Tyr-Lys-(Leu-Lys₄)₃-Leu-Lys that inhibited scavenger receptors with an IC₅₀ = 20 μM. A further decrease in PEG MW to 2 kDa increased potency further, resulting in a low molecular weight (4403 g/mol) PEG-peptide with an IC₅₀ of 3 μM. Optimized low molecular weight PEG-peptides also demonstrated potency when inhibiting the uptake of radio-iodinated DNA nanoparticles by the liver. This study demonstrates an approach to discover low molecular weight PEG-peptides that serve as potent scavenger receptor inhibitors to block nanoparticle uptake by the liver.

Effectiveness of localized ultrasound-targeted microbubble destruction with doxorubicin liposomes in H22 mouse hepatocellular carcinoma model

OBJECTIVE

In order to increase local drug concentration and reduce systemic side effects of liver cancer chemotherapy, it is desirable to develop novel non-invasive technologies for drug targeting, such as ultrasound-targeted microbubble destruction (UTMD).

METHODS

H22 hepatocellular carcinoma (HCC) xenograft transplantation model was generated in UTMD study. BALB/c mice were randomly divided into six groups: doxorubicin HCl liposomal injection (DOX), DOX + US, UTMD, DOX + UTMD, H22 liver tumor control (CH control) and blank control group. The therapeutic schedule started on day 4 after tumor inoculation.

RESULTS

Average survival time of the animal model was approximately 18 d. The UTMD therapy parameters were optimized in the H22 mouse model to be: microbubble (MB) diameter, 2.30 ± 0.25 μm; MB density, 4.0 × 10(9) bubbles/ml; treatment dose, 0.2 ml per 20 g mouse body weight; sonication frequency, 1.3 MHz; and sonication power, 2.06 W/cm(2). Mice treated with DOX + UTMD had the smallest tumor volume and weight (p < 0.001), and the highest tumor inhibition rate (p < 0.01), intratumoral DOX concentration (p < 0.001) and survival rate among all tumor-burden groups (p < 0.001). Cell viability in different treatment groups was also assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.

CONCLUSION

An improved antitumor effect was observed with the combination therapy of DOX and UTMD, as compared with treatment with DOX, DOX + US or UTMD, which implicates a novel approach for HCC treatment.

Nanoparticle ligand presentation for targeting solid tumors

Among the many scientific advances to come from the study of nanoscience, the development of ligand-targeted nanoparticles to eliminate solid tumors is predicted to have a major impact on human health. There are many reports describing novel designs and testing of targeted nanoparticles to treat cancer. While the principles of the technology are well demonstrated in controlled lab experiments, there are still many hurdles to overcome for the science to mature into truly efficacious targeted nanoparticles that join the arsenal of agents currently used to treat cancer in humans. One of these hurdles is overcoming unwanted biodistribution to the liver while maximizing delivery to the tumor. This almost certainly requires advances in both nanoparticle stealth technology and targeting. Currently, it continues to be a challenge to control the loading of ligands onto polyethylene glycol (PEG) to achieve maximal targeting. Nanoparticle cellular uptake and subcellular targeting of genes and siRNA also remain a challenge. This review examines the types of ligands that have been most often used to target nanoparticles to solid tumors. As the science matures over the coming decade, careful control over ligand presentation on nanoparticles of precise size, shape, and charge will likely play a major role in achieving success.

Structure of drug delivery DPPA and DPPC liposomes with ligands and their permeability through cells

Dipalmitoylphosphatidylcholine (DPPC) and 1,2-palmitoyl-phosphatidic acid (DPPA) liposomes, prepared by conventional rotary evaporation method, have similar structural organization, though they have significant differences. The similarity is that both types of lipids create standard bilayer liposomes with strong hydrophobic forces between lipids tails and with homogeneous bonds of hydrogen and electrostatic nature between hydrophilic lipids heads. By the calorimetric method, it has been shown that hydrophobic bonds break but liposomes' destruction does not occur by heating till 150 °C. As for bonds between lipid heads in liposomes, their cooperative destruction takes place at 41 °C for DPPC and 66 °C for DPPA liposomes. In the case of thermal distraction of DPPC liposomes, two so-called pre transitions peaks were observed before the main transition peak, which indicates that DPPC liposomes' structure is multilamellar. DPPA liposomes have one cooperative heat absorption peak, which points to a unilamellar structure of such liposomes. Substances of hydrophobic/hydrophilic nature, incorporated into the liposomes, are placed in hydrophobic or hydrophilic parts of liposomes, which lead to a change in calorimetric peak shapes and thermodynamic parameters. It has been shown that gold nanoparticles, incorporated into the DPPC liposomes, are able to enter Caco-2 cells. In contrast, these nanoparticles do not enter red blood cells.

Radiolabeled lipid nanoparticles for diagnostic imaging

BACKGROUND

Nanoparticles are increasingly being incorporated into the design of diagnostic imaging agents. Significant research efforts have been conducted with one class of lipid nanoparticle (liposomes) radiolabeled with gamma-emitting radionuclides as radiopharmaceuticals for scintigraphic imaging of cancer, inflammation/infection and sentinel lymph node detection.

OBJECTIVE

This article reviews the current literature with special emphasis on the clinical studies performed with liposome radiopharmaceuticals for detection of tumors, infectious/inflammatory sites or metastatic lymph nodes. Future uses of liposome radiopharmaceuticals are also described.

METHODS

Characteristics required of the radionuclide, liposome formulation and radiolabeling method for an effective radiopharmaceutical are discussed. A description of the procedures and instrumentation for conducting an imaging study with liposome radiopharmaceutical is included. Clinical studies using liposome radiopharmaceuticals are summarized. Future imaging applications of first- and second-generation radiolabeled liposomes for chemodosimetry and the specific targeting of a disease process are also described.

RESULTS/CONCLUSION

The choice of radionuclide, liposome formulation and radiolabeling method must be carefully considered during the design of a liposome radiopharmaceutical for a given application. After-loading and surface chelation methods are the most efficient and practical. Clinical studies with liposome radiopharmaceuticals demonstrated that a wide variety of tumors could be detected with good sensitivity and specificity. Liposome radiopharmaceuticals could also clearly detect various soft tissue and bone inflammatory/infectious lesions, and performed equal to or better than infection imaging agents that are approved at present. Yet, despite these favorable results, no liposome radiopharmaceutical has been approved for any indication. Some of the reasons for this can be attributed to reports of an unexpected infusion-related adverse reaction in two studies, the requirement of more complex liposome manufacturing procedures, and the adoption of other competing imaging procedures. Continued research of liposome radiopharmaceutical design based on a better understanding of liposome biology, improved radiolabeling methodologies and advances in gamma camera technology is warranted.

A CD1d-dependent antagonist inhibits the activation of invariant NKT cells and prevents development of allergen-induced airway hyperreactivity

The prevalence of asthma continues to increase in westernized countries, and optimal treatment remains a significant therapeutic challenge. Recently, CD1d-restricted invariant NKT (iNKT) cells were found to play a critical role in the induction of airway hyperreactivity (AHR) in animal models and are associated with asthma in humans. To test whether iNKT cell-targeted therapy could be used to treat allergen-induced airway disease, mice were sensitized with OVA and treated with di-palmitoyl-phosphatidyl-ethanolamine polyethylene glycol (DPPE-PEG), a CD1d-binding lipid antagonist. A single dose of DPPE-PEG prevented the development of AHR and pulmonary infiltration of lymphocytes upon OVA challenge, but had no effect on the development of OVA-specific Th2 responses. In addition, DPPE-PEG completely prevented the development of AHR after administration of alpha-galactosylceramide (alpha-GalCer) intranasally. Furthermore, we demonstrate that DPPE-PEG acts as antagonist to alpha-GalCer and competes with alpha-GalCer for binding to CD1d. Finally, we show that DPPE-PEG completely inhibits the alpha-GalCer-induced phosphorylation of ERK tyrosine kinase in iNKT cells, suggesting that DPPE-PEG specifically blocks TCR signaling and thus activation of iNKT cells. Because iNKT cells play a critical role in the development of AHR, the inhibition of iNKT activation by DPPE-PEG suggests a novel approach to treat iNKT cell-mediated diseases such as asthma.

Liposomal delivery of doxorubicin to hepatocytes in vivo by targeting heparan sulfate

Previous work demonstrated that liposomes, containing an amino acid sequence that binds to hepatic heparan sulfate glycosaminoglycan, show effective targeting to liver hepatocytes. These liposomes were tested to determine whether they can deliver doxorubicin selectively to liver and hepatocytes in vivo. Fluid-phase liposomes contained a lipid-anchored 19-amino acid glycosaminoglycan targeting peptide. Liposomes were loaded with doxorubicin and were non-leaky in the presence of serum. After intravenous administration to mice, organs were harvested and the doxorubicin content extracted and measured by fluorescence intensity and by fluorescence microscopy. The liposomal doxorubicin was recovered almost entirely from liver, with only trace amounts detectable in heart, lung, and kidney. Fluorescence microscopy demonstrated doxorubicin preferentially in hepatocytes, also in non-parenchymal cells of the liver, but not in cells of heart, lung or kidney. The doxorubicin was localized within liver cell nuclei within 5 min after intravenous injection. These studies demonstrated that liposomal doxorubicin can be effectively delivered to hepatocytes by targeting the heparan sulfate glycosaminoglycan of liver tissue. With the composition described here, the doxorubicin was rapidly released from the liposomes without the need for an externally supplied stimulus.

Liposomes incorporating a Plasmodium amino acid sequence target heparan sulfate binding sites in liver

Previous studies demonstrated that intravenously administered liposomes, incorporating a peptide from the Plasmodium circumsporozoite protein, accumulate rapidly and selectively in mouse liver. The present investigation was designed to determine the molecular components in liver responsible for liposome targeting. Studies of liver tissue slices demonstrated that immunoreactivity for heparan sulfate proteoglycan (HSPG), but not other tested proteoglycans, was distributed along sinusoidal borders of liver; this immunoreactivity appeared associated with nonparenchymal cells of the sinusoids and with the basolateral portion of hepatocytes. Peptide-containing liposomes bound to liver tissue in a pattern similar to the distribution of heparan sulfate immunoreactivity, either after intravenous injection of liposomes in vivo or after incubation of liposomes with liver slices in vitro. Control liposomes, without the peptide, displayed very light binding without a pattern. Pretreatment of liver slices with heparinase, but not chondroitinase or hyaluronidase, eliminated peptide-containing liposome binding, but did not affect binding of control liposomes. Coincubation of peptide-containing liposomes with heparin, but not with other glycosaminoglycans, markedly inhibited liposome binding to liver slices. N-desulfated and O-desulfated heparins individually were less effective inhibitors of liposome binding than was heparin. These results indicate that liposomes containing a peptide from Plasmodium target liver tissue by binding to HSPGs in the extracellular matrix.

Improved visualization of vessels and hepatic tumors by micro-computed tomography (CT) using iodinated liposomes

OBJECTIVE

The goal of this study was to determine whether iodinated liposomes are a suitable tracer for mice microvessel and liver imaging by preclinical computed tomography (CT).

MATERIALS AND METHODS

Iodinated liposomes were evaluated for vessel and liver imaging. A first group of nude mice was imaged by micro-CT after i.v. injection of liposomes at 1 or 2 gI/kg body weight (b.w.) for intervals up to 24 hours. A second group of mice bearing liver micrometastases was imaged after injection of liposomes at 2 gI/kg b.w. for intervals up to 24 hours.

RESULTS

Vascular enhancements of 120 +/- 8 and 322 +/- 20 Hounsfield unit (HU) were obtained after injection of liposomes at 1 or 2 gI/kg b.w., respectively. This enhancement decreased with a blood half-life of 135 +/- 10 and 86 +/- 9 minutes, respectively. Liver enhancement of 157 +/- 5 and 235 +/- 23 HU were obtained after injection of iodinated liposomes at 1 and 2 gI/kg b.w., respectively. Liver micrometastases (250 microm) were detectable after injection of iodinated liposomes at 2 gI/kg b.w.

CONCLUSIONS

Iodinated liposomes are a suitable contrast agent for vessels and liver imaging by micro-CT allowing clear vascular enhancement and detection of small liver metastases.

Effects of intravenous and subcutaneous administration on the pharmacokinetics, biodistribution, cellular uptake and immunostimulatory activity of CpG ODN encapsulated in liposomal nanoparticles

We have previously demonstrated that the immune response to an unmethylated cytidine-guanosine (CpG)-containing oligonucleotide (ODN) is greatly enhanced when encapsulated in a lipid nanoparticle (LN-CpG ODN). In this study, the pharmacokinetics, biodistribution and cellular uptake of LN-CpG ODN following intravenous (i.v.) and subcutaneous (s.c.) administration was characterized and correlated with immunostimulatory activity. It is shown that, despite dramatic differences in tissue distribution profiles and considerable differences in uptake by CD11c-positive, CD11b-positive, Mac-3-positive and CD45R/B220-positive cells following i.v. and s.c. administration, the resultant immune response is very similar with respect to levels of cellular activation (DX5, Mac-3, CD11b, CD45/B220, CD4, CD8 and CD11c) and cytolytic activity of immune cells [natural killer (NK) cells and monocytes/macrophages] in the spleen and blood compartments. Some differences in response kinetics and antibody-dependent cellular cytotoxicity (ADCC) activity were noted in the peripheral blood NK cell population. Analyses of particle biodistribution and cell types involved in uptake leads to the conclusion that the inherent ability of antigen-presenting cells (APCs) to sequester LN-CpG ODN results in efficient uptake of the particle, even when present at very low concentrations, leading to similar responses following i.v. and s.c. administration. These results contrast with the behavior of free CpG ODN, for which distinctly different immune responses are observed following i.v. or s.c. administration.

Administration of prednisolone phosphate?liposomes reduces wound contraction in a rat partial-thickness wound model

Macrophages play an important role in the inflammatory phase of wound healing and their activity regulates fibroblasts and keratinocytes. Modulation of macrophage function may result in improvement of the wound healing process. Prednisolone phosphate (PLP) encapsulated into liposomes was administered to partial-thickness wounds in rats. A single dose of 75 microg/kg, applied directly after wounding, resulted in up to a 30% reduction of wound contraction at 28 days after wounding. This effect could not be achieved in the group that was administered free PLP or liposomes containing phosphate-buffered saline to the wound. The number of myofibroblasts was up to 50% lower in wounds treated with the liposomal PLP at 4 days after wounding. The number of macrophages present in the wounds was not statistically different between groups. Most probably, the production of cytokines and growth factors by macrophages is altered after phagocytosing the liposomes, resulting in reduced wound contraction.

Effective targeting of liposomes to liver and hepatocytes in vivo by incorporation of a Plasmodium amino acid sequence

PURPOSE

Several species of the protozoan Plasmodium effectively target mammalian liver during the initial phase of host invasion. The purpose of this study was to demonstrate that a Plasmodium targeting amino acid sequence can be engineered into therapeutic nanoparticle delivery systems.

METHODS

A 19-amino peptide from the circumsporozoite protein of Plasmodium berghei was prepared containing the conserved region I as well as a consensus heparan sulfate proteoglycan binding sequence. This peptide was attached to the distal end of a lipid-polyethylene glycol bioconjugate. The bioconjugate was incorporated into phosphatidylcholine liposomes containing fluorescently labeled lipids to follow blood clearance and organ distribution in vivo.

RESULTS

When administered intravenously into mice, the peptide-containing liposomes were rapidly cleared from the circulation and were recovered almost entirely in the liver. Fluorescence and electron microscopy demonstrated that the liposomes were accumulated both by nonparenchymal cells and hepatocytes, with the majority of the liposomal material associated with hepatocytes. Accumulation of liposomes in the liver was several hundredfold higher compared to heart, lung, and kidney, and more than 10-fold higher compared to spleen. In liver slice experiments, liposome binding was specific to sites sensitive to heparinase.

CONCLUSIONS

Incorporation of amino acid sequences that recognize glycosaminoglycans is an effective strategy for the development of targeted drug delivery systems.

The use of sterically stabilized liposomes to treat asthma

Asthma is characterized by airway hyperresponsiveness, chronic inflammation, and airway remodeling, which may lead to progressive, irreversible lung damage. Liposomes have been used for the delivery of aerosolized asthma medications into the lungs. This method could facilitate sustained action of steroids while using only a fraction of the dosage and a less frequent dosing interval than conventional therapy. We describe the evaluation of the effect of budesonide encapsulated in sterically stabilized liposomes on lung inflammation and airway hyperreactivity in a mouse model of asthma. We outline the determination of markers implicated in the progression of asthma, including histopathology, eosinophil peroxidase activity in bronchoalveolar lavage, and airway hyperresponsiveness to methacholine. Weekly administration of budesonide in sterically stabilized liposomes results in a significant reduction in the total lung inflammation score, peripheral blood eosinophil counts, and the total serum IgE level, similar to that obtained with daily budesonide. Airway hyperresponsiveness to methacholine challenge decreases significantly in the group treated with weekly budesonide in sterically stabilized liposomes, while it does not decrease in the daily budesonide group.